Posted in Star Wars: Legion Official Rulings
Question: If Sabine Wren is equipped with the Darksaber and is defending against Darth Vader’s melee attack, does she roll three additional defense dice thanks to her Impervious keyword, even though the Darksaber grants her the Immune: Pierce keyword?
Answer: No. If a unit has both the Impervious and the Immune: Pierce keywords, the Impervious keyword has no effect because Pierce is not being used for that attack.
Legion HoloNet